Oxygen is produced in large quantities by the cryogenic rectification of feed air in a cold box comprising one or more columns. Prior to entering the cold box the feed air is initially processed in a feed air preparation system wherein the feed air is compressed, cooled and cleaned of high boiling impurities, such as water vapor, carbon dioxide and/or hydrocarbons, which would otherwise solidify at the low temperatures of the cryogenic rectification. Typically the feed air preparation system utilizes relatively standard equipment. However, the cold box, and in particular the column or columns of the cold box, must be designed specifically of each individual cryogenic rectification plant depending upon the desired production of product oxygen by that plant. This individual design of each individual cold box is costly and time consuming.
Accordingly it is an object of this invention to provide a cryogenic rectification system which enables one to have cryogenic rectification plants of different capacities without need for a different cold box design for each such cryogenic rectification plant.